Carbon Problems and Chlorophyll Solutions
Overview:
Students will learn how plants can sequester carbon by taking carbon dioxide
from the atmosphere through the process of photosynthesis and storing it in
the biosphere. This will be accomplished through an introduction to carbon
dioxide’s role in the atmosphere and how carbon enters the biosphere
through photosynthesis. This will be followed by a hands-on experiment to
extract and separate chlorophyll and pigments found in leaves.
Keywords:
Carbon cycle, photosynthesis, chlorophyll, cellular respiration, atmosphere,
biosphere, sequester
Age / Grade Range:
5th – 12th
It has been shown that higher levels of carbon dioxide in the Earth’s
atmosphere can affect climate change by trapping the reflected heat of the
sun within the atmosphere. Carbon dioxide can be removed from the
atmosphere by plants and other organisms through a process known as
photosynthesis. Photosynthesis is also the main process that allows carbon
atoms to enter into the biosphere. Carbon is necessary to fuel life processes
and provide structure for all living things.
Background:
Most plants appear green because of a pigment called chlorophyll.
Chlorophyll absorbs light from the red and blue range of the visible light
spectrum; however, green is not absorbed well. Therefore, the green portion
of the light spectrum is mostly reflected, which gives plants their green color.
Not all green light is reflected though. There are other pigments such as
carotenoids and xanthophylls which can help to utilize a broader portion of
the light spectrum. Typically, these pigments occur in lesser amounts than
chlorophyll, and give plants various shades of green.
During photosynthesis, sunlight is absorbed by chlorophyll, which provides
the energy to take carbon dioxide and water molecules out of the atmosphere
and combine them. This produces sugar and oxygen molecules.
A common sugar is glucose. 6 carbon and 6 water molecules are necessary to
produce one molecule of glucose. As a byproduct, 6 molecules of oxygen are
also produced. This process can be expressed in the chemical equation:
6CO2 + 6H2O + sunlight = C6H12O6 + 6O2


Plants can then use the glucose to provide energy for life functions, or the
energy may be passed on to animals that ingest the plants. The chemical
energy stored in glucose is utilized by an organism through the process of
cellular respiration. When cellular respiration occurs, the cells within an
organism break the bonds of sugar molecules or other nutrients to form
adenosine triphosphate (ATP). Cells can then further break the bonds of ATP
to fuel cellular activities. Cellular respiration is the main way that an
organism uses the biochemical energy in nutrients to provide energy for life
functions. Cellular respiration also transfers carbon from the biosphere to the
atmosphere. The chemical equation for cellular respiration of glucose is:
C6H12O6 + 6O2 = 6CO2 + 6H2O + ATP
Next Generation
Science Standards
Core idea: Physical Sciences
PS1.A: Structure and Properties of Matter
PS1.B: Chemical Reactions
PS3.D: Energy in Chemical Processes and Everyday life
Core idea: Life Sciences
LS1.B: Growth and Development of Organisms
LS1.C: Organization for Matter and Energy Flow in Organisms
LS2.B: Cycles of Matter and Energy Transfer in Ecosystems
Core idea: Earth and Space Sciences
ESS3.D: Global Climate Change
In this lesson, students will learn about how photosynthesis sequesters
carbon from the atmosphere into the biosphere. Pigments such as
chlorophyll, carotenoid, and xanthophyll absorb energy from sunlight which
allows photosynthesis to take place. Students will use the chemical, acetone,
to extract pigments from a plant’s leaves. Coffee filters or chromatography
paper will then be used to separate the pigments for observation.
Goals:
Essential questions:
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How does carbon dioxide affect global climate change?
How does carbon enter the biosphere?
What happens during photosynthesis?
Where does photosynthesis occur?
How does carbon move from the biosphere to the atmosphere?
Enduring Understandings
Objectives:
Materials:
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Students will understand that carbon can move from the atmosphere
into the biosphere through photosynthesis.
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Students will understand that photosynthesis takes place in
chlorophyll.
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Students will understand that plants appear to be particular colors
because the light being reflected is not being used for photosynthesis.
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Acetone
Glass or metal mixing bowl
Spoon
250 ml glass graduated cylinder or tall glass
50 ml glass graduated cylinder
Coffee filter or chromatography paper
Scissors
Toothpick
Plastic wrap
5 spinach leaves
Goggles
Gloves
A stick or piece of firewood
Collect enough supplies for students to be able to work independently or in
very small groups.
Set up:
Classroom Time:
Introduction
(Engage):
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Length of experiment: 45 minutes
Length of introduction: varies depending on teaching goals
Using the attached greenhouse effect visual or a similar diagram, explain to
the students how carbon dioxide plays a role in global climate change.
However, carbon is also a very important atom for the biosphere. It provides
energy and structure to all living things.
Place a piece of wood on a table for all students to see. Initiate a discussion
based on where the wood got its mass, size, shape, and volume. Help steer the
conversation to carbon dioxide from the air.


Now brainstorm with the students how the carbon that now makes up the
mass of the wood came out of the air and entered into the plant. The answer
is photosynthesis.
Pass around some of the spinach leaves and have the students explore them:
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Where does photosynthesis occur?
Why are the leaves green?
Let the students know that we are going to take a closer look at the
chlorophyll and other pigment in the leaves. These are what give the leaves
their color and also where photosynthesis takes place.
Before conducting the experiment, talk to students about safety and handling
the materials.
1) Give each group a mixing bowl, a spoon, a tall glass, a half inch wide
strip of coffee filter, scissors, a toothpick, some plastic wrap, and five
spinach leaves.
2) Have the students cut the spinach leaves into small pieces and place
them in the mixing bowl.
3) Add 15ml of acetone to the mixing bowl and have students muddle the
spinach leaves with a spoon for 5 minutes. Then allow the mixture to
sit for an additional 5 minutes (this is a good time for a discussion
question).
Activity (Explore):
4) Add about 20ml of acetone to the bottom of the tall glass.
5) By this time, the pigments will have started dissolving into the
acetone. Take a coffee filter strip and add some of the pigments and
leaf pulp to the bottom of the strip. Roll the top of the strip around the
toothpick so that the toothpick will lie across the top of the tall glass
with the coffee filter hanging down into the glass. Only the very
bottom of the coffee filter should touch the acetone.
6) Cover the tall glass with plastic wrap and wait 20 minutes (another
good time to lead a discussion). The coffee filter will act as a wick,
drawing acetone and pigments towards the top of the filter. After 20
minutes has passed, you should be able to see several different lines of
colors developing from the pigments. Darker green lines are
chlorophyll a, lighter green are chlorophyll b. Orange carotenes, yellow
xanthophylls and red/purple anthocyanins may also be present.


Chlorophyll pigments are where photosynthesis takes place, therefore plants
have many chlorophyll pigments. Plants may have several different types of
chlorophyll that are slightly different shades of green. This is so that the plant
can utilize a wider range of sunlight.
Explanation:
Other pigments, such as carotenes, xanthophylls, and anthocyanins may also
be present in leaves, but occur in much smaller quantities. These pigments
can help capture additional energy from sunlight to help drive
photosynthesis, but they do not photosynthesize.
What do the students think would happen if they ran the same experiment
with different colored leaves such as a purple cabbage or a red leaf Japanese
maple?
Elaboration:
How would the pigments from plants in a sunny area differ compared to the
pigments from plants in a shady area?
How might this experiment look in the fall when leaves are starting to change
color? Why do the students think the leaves change color?
Have the students tell the tale of a carbon atom travelling from the
atmosphere to an animal. This could be accomplished in several different
ways.
Evaluation:
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Writing a story in a journal
Creating a storyboard
Developing a skit to act out in front of the class
Depending on your personal learning objectives, you may want to review
particular vocabulary words or processes that you would like them to include
in the evaluation


Additional resources:
 Chlorophyll chromatography experiment video:
https://www.youtube.com/watch?v=jiPd5CkCkkU
 Carlton College: Earthlabs – Climate and the Biosphere:
http://serc.carleton.edu/eslabs/weather/index.html
 Carlton College: Earthlabs – Climate and the Carbon Cycle:
http://serc.carleton.edu/eslabs/carbon/index.html
 Caltech: Chromatography of Plant Pigments lesson plan:
http://sunlight.caltech.edu/leoleary/06_Biology_lesson_plan.pdf
 Carbon Cycling: Environmental Processes that Change Our World:
https://edr1.educ.msu.edu/EnvironmentalLit/publicsite/files/CarbonCycle
/CC%20TeachingExperiment/0910%20Teaching%20Materials/carbon%20cycling/1109_CarbonCycle_HS_T
eacher.doc